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Shortest Path IEEE 802.1aq Overview

APRICOT/Hong Kong/Feb 24th 2011

Peter Ashwood-Smith [email protected] Fellow Abstract

802.1aq Shortest Path Bridging is being standardized by the IEEE as an evolution of the various spanning tree protocols. 802.1aq allows for true shortest path routing, multiple equal cost paths, much larger layer 2 topologies, faster convergence, vastly improved use of the mesh topology, single point provisioning for logical membership (E-LINE/E-LAN/E-TREE etc), abstraction of attached device MAC addresses from the transit devices, head end and/or transit replication , all while supporting the full suit of 802.1 OA&M.

Applications consist of STP replacement, Data Center L2 fabric control, L2 Distributed Exchange point fabric control, small to medium sized control planes. L2 network backhaul….

2 Outline

• Challenges • What is 802.1aq/SPB • Applications • How does it work • Status

3 Challenges

• L2 networks that scale to ~1000 bridges. • Use of arbitrary mesh topologies. • Use of (multiple) shortest paths. • Efficient broadcast/multicast routing and replication points. • Avoid address learning by tandem devices. • Get recovery times into 100’s of millisecond range for larger topologies. • Good scaling without loops. • Allow creation of very many logical L2 topologies (subnets) of arbitrary span. • Maintain all L2 properties within the logical L2 topologies (transparency, ordering, symmetry, congruence, shortest path etc). • Reuse all existing Ethernet OA&M 802.1ag/Y.1731

“Make a network of switches look like a single switch!” 4 Example problems of scaling up Native Ethernet 2- poor routes 1- Can’t use these links

Source

ROOT A1.. A100

Dest

3 – Must learn A1..A100 5 Outline

• Challenges • What is 802.1aq/SPB • Applications • How does it work • Status

6 What is 802.1aq/SPB • IEEE protocol builds on 802.1 standards • A new for Q-in-Q and M-in-M – Leverage existing inexpensive ASICs – Q-in-Q mode called SPBV – M-in-M mode called SPBM • Backward compatible to 802.1 – 802.1ag, Y.1731, suite • Multiple loop free shortest paths routing – Excellent use of mesh connectivity – Currently 16, path to 1000’s including hashed per . • Optimum multicast – head end or tandem replication 7 What is 802.1aq/SPB (cont’d) • Light weight form of traffic engineering – Head end assignment of traffic to 16 shortest paths. – Deterministic routing - offline tools predict exact routes. • Scales to ~1000 or so devices – Uses IS-IS already proven well beyond 1000. – Huge improvement over the STP scales. • Good convergence with minimal fuss – sub second (modern , well designed) – below 100ms (use of hardware multicast for updates) – Includes multicast flow when replication point dies. Pre-standard seeing 300ms recovery @ ~50 nodes. • IS-IS – Operate as independent IS-IS instance, or within IS-IS/ IP, supports Multi Topology to allow multiple instances efficiently. 8 What is 802.1aq/SPB (cont’d)

• Membership advertised in same protocol as topology. – Minimizes complexity, near plug-and-play – Support E-LINE/E-LAN/E-TREE – All just variations on membership attributes. • Address learning restricted to edge (M-in-M) – FDB is computed and populated just like a . – Unicast and Multicast handled at same time. – Nodal or Card/Port addressing for dual homing. • Computations guarantee ucast/mcast… – Symmetry (same in both directions) – Congruence (unicast/multicast follow same route) – Tune-ability (currently 16 equal costs paths – opaque allows more)

9 End result - Visually

All links usable

Multiple Shortest Path routing&Ethernet OA&M 10 SPF trees form multicast template

Shortest Path First Tree becomes template for multicast tree and is pruned automatically to proper membership. 11 Edge Learning - Visually

Dst.B-MAC Src.B-MAC

B-VLAN

801.1AH/ I-SID Dst.C-MAC

Src.C-MAC :B

C-VLAN

Payload

Learn A via 1!

A|B? FIB To: 20 Hop => To: 1 next Hop <= :A Learn B via 20! Learning restricted to edges and only where I-SID tree reaches. Mac-in-Mac encap. 12 Animation for 8 member E-LAN ‘255’

I-SID 255 has 8 members

Shown are all routes used by this I-SID in pink.

Two trees shown blue/green.

Note symmetry of trees between source/dest

If transit multicast selected fork points in trees are replication points.

13 Outline

• Challenges • What is 802.1aq/SPB • Applications • How does it work • Status

14 Applications

• Anywhere that Spanning Tree is being used. Take existing STP/MSTP based network and migrate to Shortest Path Routing.

• Ethernet Exchange Points Big distributed switch to interconnect hundreds of different customers cheaply with L2VPNs.

• Metro Ethernet Light weight metro protocol, L2VPN solution simpler than VPLS with lower capex/opex.

• Wireless backhaul Use of L2VPN for LTE backhaul

15 Application Data Center Treat DC network as one big L2 switch by combining 100’s of smaller switches in ‘non blocking’ topology – why?

• Any server anywhere.

• Any router anywhere.

• Any appliance anywhere.

• Any VM anywhere. - Any IP address anywhere. - Any subnet anywhere. BIG L2 • Any storage anywhere.

• Minimal congestion issues.

• Total flexibility for power use 16 Application Data Center

• Multiple shortest path routing • inter server traffic

• Deterministic traffic flows.

• Flexible subnet – expand/shrink anywhere. • Virtualization operates in subnet.

• Fully compatible with all 802.1 Data Center Bridging protocols & OA&M. 1.1.1.* • Address isolation through m-in-m 1.1.2.* • Fast recovery

• No loops

17 Application Data Center (cont’d)

• Totally compatible with Vmware server functions: • OA&M, motion, etc. • Apps that sit on Vmware ‘just work’.

• Fully compatible with all load balancer ADC appliances.

• VRRP transparent (primary/stdby rtr per subnet) or proprietary variations on same protocol.

• Compatible with emerging Inter DC overlay work or Inter DC L2 tunnels.

18 Non Blocking Switching Cluster

A1 A2 A15 A16 Good

numbers 32 x 100GE “16” & “2” levels. 16 x 32 x 100GE = 51.2T using 48 x 2T switches So 102T

16 x 100GE

160 x 10GE B1 B2 B3 B4 B29 B30 B31 B32

5120 x 10GE

S1,1 S1,160 S3,1 S3,160 S32,1 S32,160

• 48 switch non blocking 2 layer L2 fabric • (16 x 100GE per Bn )x32 = 512x100GE = 51.2T • 16 at “upper” layer A1..A16 • 160 x 10GE server links (UNI) per Bn • 32 at “lower” layer B1.. B32 • (32 x 160)/2 = 2560 servers @ 2x10GE per • 16 uplinks per Bn, & 160 UNI links per Bn • 32 downlinks per An 100+ Terra non blocking fabric (if switches non blocking) 19 ECMP in DC

Can get perfect balance down spine of a two layer 16 ECT L2 Fabric. Shown Are all 16 SPF’s from 2<->24

16 different SPF trees Each use different spine as replication point. Shown is one of the 16 SPF’s from/to 1. 20 Outline

• Challenges • What is 802.1aq/SPB • Applications • How does it work • Status

21 How does it work? • From Operators Perspective - Plug NNI’s together - Group ports/c-vlan/s-vlan at UNIs that you want to bridge (224 groups=‘services’ m-in-m mode.) - Assign an I-SID to each group.. - Use your .1ag OA&M • Internally - IS-IS reads box MAC, forms NNI adjacencies - IS-IS advertises box MACs (so no config). - IS-IS reads UNI port services and advertises. - Computations produce FIBs that bridge service members. 22 Data Path (M-in-M mode)

• C-vlan/S-vlan or untagged traffic arrives at UNI • Its encapsulated with B-SA of bridge • Its encapsulated with I-SID configured for group • Its encapsulated with B-VID chosen for route • C-DA is looked up, if found B-DA is set • C-DA not found, B-DA is multicast that says: • Multicast to all other members of this I-SID group from ‘me’. Or can head-end replicate over unicast. • C addresses to B address association learned at UNI only.

23 FDB (unicast M-in-M mode)

• A unique shortest path from node to all others is computed.

• BMAC of other nodes installed in FIB pointing to appropriate out .

• Above is repeated for 16+ shortest paths each causes a different B-VID to be used.

• Symmetry is assured through special tie- breaking logic. 16+ different tie-breaking algorithms permit 16+ different shortest paths.

24 FDB visually: ucast m-in-m mode

:2 :3 9 3 :1 6 :4 10 :6 :5

MAC | BVID | IF MAC | BVID | IF :4 | 1 | 9 :1 | 1 | 3 :4 | 2 | 9 :1 | 2 | 6 :4 | 3 | 10 :1 | 3 | 3 :4 | 4 | 10 :1 | 4 | 6

25 FDB (mcast M-in-M mode)

If no services require tandem replication there is no tandem FDB: Very VPLS like .. Pretty boring….head replication over unicast paths Else (mp2mp) If my node is on a unique shortest path between node A , (which transmits for a group I) and node B (which receives on the same group I), then: merge into the FDB an entry for traffic from DA ={ A/Group I} to the interface towards B.

26 FDB visually: mcast m-in-m mode

I=255 :2 :3 I=255 9 :1 :4 I=255 10 6 :6 5 :5

MMAC |BVID|IF MMAC |BVID| IF {:1/255}|4 |10 {:1/255}|4 |5,6

27 802.1aq OAM capabilities 1. Continuity Check (CC) a) Multicast/unidirectional heartbeat b) Usage: Fault detection 2. Loopback – Connectivity Check a) Unicast bi-directional request/response b) Usage: Fault verification 3. Traceroute (i.e., Link trace) a) Trace nodes in path to a specified target node b) Usage: Fault Isolation 4. Discovery (not specifically supported by .1ag however Y.1731 and 802.1ab support it) a) Service (e.g. discover all nodes supporting common service instance) b) Network (e.g. discover all devices common to a domain) 5. Performance Monitoring (MEF10 and 12 - Y.1731 for pt-pt extending to pt-mpt and mpt-mpt) a) Delay, Frame Loss, Frame Delay Variation (derived) b) Usage: Capacity planning, SLA reporting

28 Outline

• Challenges • What is 802.1aq/SPB • Applications • How does it work • Status

29 Status

• DEPLOYMENTS: • Pre-standard SPBM live customer networks: • 3 carrier (20+nodes) • 5 enterprise • 3 dc deployments

• SPBM Data path (PBB) and OA&M of course has large number of deployments world wide.

• INTERWORKING: • Avaya (ERS 8800) + Huawei (S9300) successful Inter-working including full line rate data paths + L2 ping x 5 physical 32 logical nodes • IETF: • In IESG last call, RFC imminent ~1Q 11

• IEEE: • Expected completion ~3Q 11.

30 References

“IEEE 802.1aq” : www.wikipedia.org: http://en.wikipedia.org/wiki/IEEE_802.1aq Good overview, up to date with lots of references / tutorial videos all linked. http://www.ietf.org/internet-drafts/draft-ietf-isis-ieee-aq-04.txt The IETF IS-IS draft soon to be RFC.

“Shortest Path Bridging – Efficient Control of Larger Ethernet Networks” : IEEE Communications Magazine – Oct 2010

“Provider Link State Bridging” : IEEE Communications Magazine V46/N9– Sept 2008

Thank-You

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